Fire blazes through the Glasgow School of Art’s Mackintosh building on 16 June 2018. ‘The heart of Glasgow’s Mackintosh legacy has been ripped away.’ Photograph: Scottish Fire Service Handout/EPA

The gutting by fire of Glasgow School of Art’s Mackintosh building is a huge loss to Scotland and the world. The highly distinctive structure, completed in 1909, was Charles Rennie Mackintosh’s masterpiece. It is also the home of one of the UK’s most important art schools and a place beloved by students, many of whom have spoken in recent days of their shock and sadness. Neither the fact that the art school has a strongly Scottish identity, nor divisions between Scottish and UK politicians over Brexit, should obscure a shared sense of deep dismay.

That anger was also being expressed even before the fire was fully out is understandable, and right. A costly and painstaking £35m restoration was nearing completion, with timbers to match the originals sourced from a Massachusetts mill. An exhibition at Kelvingrove Museum, planned to coincide with the 150th anniversary of the architect’s birth, opened a few weeks ago. The refurbished Mackintosh-designed Willow Tea Rooms reopens in a fortnight; another tea room is one of the centrepieces of the new V&A in Dundee. Mackintosh was a one-off, his career a brilliant chapter in the story of Scottish and British art and design. Now the heart of Glasgow’s Mackintosh legacy has been ripped away.

Kier Construction, the contractor that had day-to-day charge of the site, has a case to answer. Questions about fire prevention and why a sprinkler system wasn’t operational require an answer. But the School of Art too must account for its stewardship of the Mack. The 2014 fire was caused by a projector catching light, after flammable material that was part of a student project was placed nearby. Then, neither an individual act of negligence nor a broader failure of process or leadership was blamed. In the aftermath of this second fire, responsibility must not be ducked. The debate about what happens next is already live, with the School of Art’s bosses and city council insistent that the building will not be written off, while architects query whether a second attempt at a reproduction is a good idea. Buildings such as Dresden’s Frauenkirche have been entirely reconstructed. Others such as Berlin’s Reichstag have been partially conserved and combined with new elements (Norman Foster’s glass dome).

Which is the better course in this case, and where will the money will come from? Raising £35m for the last rebuild required a huge effort. This time the cost is estimated at three times that. The UK government has said it will contribute, as it should, given the school’s importance. But culture and higher education are devolved areas. Whether the people of Glasgow, and Scotland, want to spend tens of millions of pounds on rebuilding an art school – and whether they want the Mack back just as it was, or something else – is a question that won’t have an easy answer. Whether or not a public inquiry into the fire goes ahead – and Scottish secretary David Mundell does not support one – some forum in which the Mackintosh building’s future can be openly discussed must be found.